A lubricant injector used at a location at which mechanical friction occurs in a normal mechanical device for industry has become widespread and is being used in many industrial fields. Although the use of the lubricant injector is increasing, problems may occur when the lubricant injector is used in industrial settings. These problems occur due to the following reasons.
First, a lubricant injector is a device for injecting lubricant, that is, grease, and the grease is made up of a thickener, a base oil, and an additive that are combined physically but not chemically. That is, the thickener functions to hold oil, which can be released from the thickener when a force is applied thereto. This idea is analogous to the idea of a sponge holding water and then releasing the water when squeezed. Accordingly, when a predetermined pressure or stress is applied to grease, oil is automatically separated from a thickener. Measuring the separation of the oil from the thickener is referred to as bleeding. The higher the bleeding, the more easily oil separates from the thickener.
Accordingly, the lubricant injector normally uses the following two methods according to a method of discharging grease by applying pressure to the grease. One method is a gas discharge method normally using nitrogen gas or hydrogen gas, in which when gas, regardless of being nitrogen gas or hydrogen gas, is generated from a gas generating device, and the generated gas regularly applies pressure to a piston, grease is discharged by the pressure. When the gas continuously presses the piston for a long period of time, from one month to one year, oil is separated from grease, and thus the oil comes gradually out from an inside of a container. In the end, at one point, only a thickener is left and hardened in the container like mud, and thus it becomes impossible to discharge the thickener any longer by using pressure of the gas. In this case, since the grease may be misperceived to remain at normal levels in the container, the grease may be neglected, thus possibly leading to bearing damage.
Next, a mechanical discharge method developed to overcome a disadvantage of the above-mentioned gas discharge method includes two methods widely used in various industrial fields. One method is a screw down method, and the other method is a method using a positive displacement pump. Although the screw down method is relatively advantageous in terms of bleeding, the screw down method has a limitation in that it has low grease discharge pressure.
According to the related art having the above-mentioned structure disclosed in U.S. Pat. No. 7,229,941 B2, a wedge-shaped slide surface is attached to a lower part of a gear wheel, the wedge-shaped slide surface being connected to a ram, and rotation of the gear wheel allows the ram to move up and down along an opposing wedge-shaped slide surface that is connected to the ram and positioned under the wedge-shaped slide surface. As the ram moves up and down, grease is compressed and discharged. Accordingly, a structure of a lubricant injector using the screw down method is very complicated, and is high in manufacturing cost and energy consumption. Further, it is necessary to lift a wedge slide by using the force of a spring, and high resistance occurs in the case of low temperature or slow movement of grease according to viscosity of the grease, thus the amount of discharged grease may change. Additionally, since a storage chamber for storing lubricant is configured to have a dual structure made up of an inner container and an outer cover, changing the storage chamber causes inconveniences, and it is structurally impossible to feed oil.
The method using the positive displacement pump developed to solve a problem of the screw down method is advantageous in that the positive displacement pump can obtain a higher discharge pressure by suctioning and compressing grease after connecting a pump to a small motor. However, since a spring continues to apply pressure to the grease from a part above the pump such that the grease is efficiently introduced into the pump, separation of oil from the grease occurs at one point as in the gas discharge method, and when the separation of oil occurs, grease movement slows down. Accordingly, since the grease is prevented from being efficiently introduced into the pump and thus an injection hole is clogged, grease discharge is stopped.